A cochlear implant is a surgically implanted electronic device that resides in the cochlea of a patient's ear and provides a sense of sound to the patient who is profoundly deaf or severely hard of hearing. The present specification relates to such neural stimulators and, particularly, to cochlear implant systems that include electrode arrays for stimulation of a patient's cochlea. In a typical cochlear implant, an array of electrode contacts are placed along one side of an elongate carrier or lead so that when the array is implanted within one of the cochlear ducts, such as the scala tympani, the electrode contacts are positioned in close proximity to the cells that are to be stimulated. This allows such cells to be stimulated with minimal power consumption.
To maximize the benefit of the surgery for the patient, it is important to preserve the residual hearing of the patient and to maximize the long term effectiveness of the cochlear implant. As the cochlear lead is inserted through the tissues in the head and into the cochlea, there can be mechanical damage to the surrounding tissues, subsequent inflammation, and possibly damage to the delicate structures within the cochlea. Additionally, various autoimmune reactions can occur in response to the presence of the cochlear lead in the cochlea. These autoimmune reactions can include growth of tissue around the cochlear implant and eventual ossification. This tissue growth can act as a barrier between the electrodes of the cochlear implant and the target nerves. This can lead to a degradation of the performance of the cochlear implant over time.
Throughout the drawings, identical reference numbers designate similar, but not necessarily identical, elements.